Keys Energy Services is warning customers that a familiar scam is back just in time for the holidays.

If someone calls threatening to cut power to your home or business, it's a scam. Hang up, call your utility and report the phone call to police, said Keys Energy spokesman Julio Torrado.

"This is never something we would do in this way," Torrado said.

The fraud was first reported over the summer and occurred at many businesses, mainly restaurants, where workers and owners are often busy and don't have time to double-check claims being made by criminals on the phone, Torrado said.

Two cases arose anew in the past two weeks, but those were reported by private residents, Torrado said.

Neither power utility in Monroe County -- Keys Energy Services, which covers Key West to the Seven Mile Bridge, or Florida Keys Electric Co-op, which covers Marathon to Key Largo -- makes any such calls without sending a series of mailings first, officials said.

"Every couple of months we're seeing this scam return, and we're getting calls again," Torrado said. "The one common thread is that people are being asked to wire money. We would never tell anyone to proactively go to a specific store and send us a money gram."

There have been three such cases reported to the Florida Keys Electric Co-op in the past few days, said spokeswoman Nikki Dunn.

"We're experiencing another wave of this and having the same issues since the summer," Dunn said. "I actually just talked to one customer today. If someone calls you, always hang up and call our office, and never give any information to anyone over the phone unless you initiate the contact."

Another red flag is that most of the calls come after business hours, Torrado added.

"It seems like they're making the rounds to see what they can get just in time for the holidays," he said.

The scam is not new and has been occurring nationwide, said Monroe County Sheriff's Office spokeswoman Becky Herrin.

Officials urged customers to report the scam to the utilities and to Key West police at 305-809-1111, or the sheriff's office at 305-292-7000.

The direct line for Keys Energy Services is 305-295-1023; FKEC's is 305-852-2431.